Collapsible building drum



Jan. 29, 1952 H. c. HoDGKlNs 2,583,650

COLLAPSIBLE BUILDING DRUM Filed Feb. 25, 1950 4 Sheets-$heet l Jan. 29, 1952 H, c. HoDGKlNs 2,583,650

COLLAPSIBLE BUILDING DRUM Filed Feb. 25. 1950 4 Sheets-Sheet 2 .ATTORNEY Jan. 29, 1952 H. c. HoDGKlNs COLLAPSIBLE BUILDING DRUM 4 Sheets-Sheet 3 Filed Feb. 25, 1950 Jan. 29, 1952 H. c. HQDGKINS 2,583,650

COLLAPSIBLE BUILDING DRUM Filed Feb. 25, 195o 4 Sheets-Sheet 4 BY 15mg www ATTORNEY Patented Jan. 29, 1952 UNITED STATES PATENT OFFICE COLLAPSIBLE BUILDING DRUM Hollis C. Hodgkins, Eau Claire, Wis., assignorto United States Rubber Company, New York,` .N. Y., accorporation of New Jersey Application February 25, 1950, Serial No. 146,312

14 Claims.

The present `invention Arelates to a building drum for use in building tire caslngs, belt carcasses, vessels, or other articles of fabric and rubber commonly assembled lingenerally band form. More particularly it relates to a rotatable building drum of the type which may be collapsed to permit easy removal Aof thecompleted article.

It is an `object of the invention to provide a new and improved building drum of the collapsible type which is of rugged yet simplified construction and in which wear ofthe parts does notadversely affect an accurate collapsing and expanding action of the drum.

Another object of the invention is the provision of a collapsible building drum `so ccnstructed and arranged that the operating linkage for expanding and collapsing the drum is not adversely affected by centrifugal forces developed as the drum rotates.

Another object is the provision of a collapsi ble drum that can be attached to and detached from a tire building machine shaft with ease and accuracy but without undue wear or strain on the attaching means.

Still another object of the invention is to\pro vide a collapsible building drum in which the collapsing parts are symmetrically arranged about the axis of the drum thereby providing for interchangeability of the parts of the drum and the collapsing mechanism.

A further object of theinvention is toprovide an improved collapsible building drum which may be adjusted to build articles of a range of sizes and shapes and in which `the necessary adjustments may be easily and quickly made.

Still a further object is the provision of an improved building drum which can be collapsed Vand expanded rapidly without subjecting the parts to shock.

These and other objects and-advantages will appear more fully in the following detailed description when considered in connection Vwith the accompanying drawingain which:

Fig, 1 is a sectional view, taken substantially along the lines I-I of Fig. 2, of a building drum embodying the features of the present invention, certain parts being broken away to reveal the structure in more detail;

Fig.,2 is an end view of the drum with parts broken away;

Fig. 3 is aside view Yof the drum, taken partly in section, substantially along the lines 3-3 of Fig. 4, in the collapsed condition;

Fig. 4 is an end view of the drum in the collapsed condition;

Figs. 5 and 6 areperspective views ol' parts of the mechanism for controlling the collapse of the drum; and

Fig. 7 is a fragmentary sectional view `of an edge portion of the drum illustrating a means for changing therwidth 'oi 'the building surface of the drum.

Referring to the drawings, and particularly to Fig. 2, the rotatable tire building drum shown therein comprises a series ofsmaller or minor arcuate sections, or` key segments IIl, II and I2, and a series of larger ormajor arcuate sections or segments I3, I4 and l'alternately 'disposed with respect to said ykey segments, and forming therewith a 'smooth contiguousrcylindrical building surface ,when the drum 1s inthe expanded condition.

The entire drum structure is supported from a central hub memberIG (Figs. 1 and 3) having,

s as shown ingreatest detail in Fig. 1, a section I'E of reduced diameter, wherein the means vfor actuating the drum, `such as a pneumatic cylinder I8, is preferably located. The key segments lil, Il and I2 are supported in part from a collar is which is xed by a set screw 240 to the reduced portion I'I of the hub I6. The collar I9 has keyways 2| (Fig. 5) wherebyit is keyed to the `hub to prevent it from rotating relative thereto.

For the purpose of attaching the smaller or key segments I0, II and I2 to the fixed collar I9 in a radially movable manner, collapsible toggle links 25 and 25 are provided in associa tion with each of said segments. A lug 21 (Figs. l and 5) extending from the collar I9 is en gaged by the inner end of link 25 and is pivotally secured thereto by a pin 28 (Fig. 1) passing through a hole 29 (Fig. 5) in the lug. A screw Sil (Fig. 1) passing through the lug 2I permits tightening of the pivot pin 28by squeezing togetherthe walls of a slot`3l (Fig. 5) provided in ,the lug for this purpose. The link 26 is attached to a lug 32 on the inner surface of segment II by a pivotpin 33 in a similar manner.

Forked ends of links'25 and `'M5 intermediate the hub and segment are both joined by a similar pivot pin 35 to'an actuating toggle arm36 extending generally axially of the drum, This toggle arm 36 is, in turn, pivotally joinedin like manner to radially `extending lugs 31 on an axially movable actuating `plate 38. It will`be ,understood that each of the other two key `segments Iiland I2 are attached to the Yactuating plate 35 and to the hub collar I9 by a pivotal link and toggle `arm arrangement `identical `to that just described in association `with key `segs- `extending arms 4 I.

ment I I. It should also be noted that for larger size drums, I may provide more than one such pair of links 25 and 26 for each key segment, the better to support and collapse the segments.

Considering now the structure by which the larger segments, I3, I4 and I5 are collapsibly supported from the hub of the drum, there is provided, in association with the iixed hub collar I9, a rotatable collar 46 having generally radially This spider-like member, as shown in Fig. 6, has a central aperture 42 through which the hub portion I'I extends, and is equipped on one face with axially projecting lugs or stop members 43, designed to ride in arcuate slot-like guideways 44 (Fig. 5) formed in each end face of the xed hub collar I9 by axially extending projections or stops 45 thereon. In this way, spider member 48 is capable o1" limited rotation with respect to the hub of the drum.

As is shown in Fig. 1, one such rotatable spider 4I] engages one end of the fixed collar I9, while another such rotatable collar or spider 46, of identical construction, but facing in the opposite direction,.engages the other end of collar i9. A cylinder head member 41 on the end of the actuating cylinder I8, and a flange portion 48 extending from the hub, maintain the spiders 49 and 46, respectively, in place on the hub. The spiders are therefore unable to move axially of the drum. Spider 46 also has generally radially extending arms 49, similar to the arms 4I of spider 48, but the arms 49 are canted in the opposite direction with respect to arms 4i, asrappears most clearly in Fig. 2, by reason of the fact that the two spiders are oppositely disposed in assembly.

Each arm 4I of the spider 4`is pivotally joined or fulcrumed to a yoke-like connecting fork, or control link 53, which serves pivotally to connect the key drum segments to the larger drum segments in such a manner as to transmit the de- -isired collapsing movement from the key segments to the larger segments, as will be described later. The yoke or control link 53 fits into the forked end 54 of arm 4I and is joined thereto by a fulcrum pin 55 passing through holes 56 in the fork 54 and hole 51 in the yoke 53 (Fig. 1) whereby the forks are enabled to swing or pivot generally radially of the drum in a plane transverse to the axis of the drum. A set screw 58 threaded into the arm 4I permits tightening of Ythe pivot pin in place in the usual manner. Bushings 59 of suitable bearing material are provided in the holes 56 as shown for smooth operation of the pivotal joints.

One'fork or arm 6I of the control yoke 53 is pivotally attached to projecting lugs 62 on the inner surface of a larger segment I3, by means of a pivot pin 63 passing through holes 64 in the lugs-and hole B in the arm 6I. The usual set screw 66 and bushings 6l of bearing metal are provided. The other fork or arm 68 (Fig. 2) of the yoke 53 is pivotally connected to a key segment I8 through a short auxiliary tie link 18. The manner in which one end of the auxiliary tie link is pivotally joined to arm68 by a pivot pin 1I, and the manner in which the other end of the auxiliary tie link is pivotally joined to lugs 12 on the key segment I6 by a pivot pin 'I3 is best seen in the broken-away portion of Fig: 2.

`In a similar manner, each of the arms 49 of the spider 46 has a control yoke 'I5 and an auxiliary ti'e'link '16, (Figs. 1 and 2), all pivotally assembled as described in connection with control yokes 53 and tie links ll). However, it will be seen by inspection of Fig. 2 that the control yoke 53 and control yokes 'I5 connect the key segments to larger segments located at opposite sides of the key segments. In other words, control yokes 53 bridge alternate bevelled joints 'Il between segments, and the control yokes 15 bridge intermediate bevelled joints 18. This manner of assembly is relevant to the opposite rotation of the spiders 48 and 46 with respect to each other during collapse and expansion of the drum, as will be described in greater detail below.

For drums of larger size, I may provide more than one pair of rotatable collars or spiders 48 and 46 with associated connecting yokes, to give additional support to the larger segments.

To further guide the movement of the larger segments during the collapsing and expanding operation, a telescoping guide assembly is assoelated with each segment. Such assembly comprises a hollow cylinder 86 (Fig. 1) threaded at its base 8IV into a suitably threaded radial hole 82 (Fig. 5) in the xed collar I9. A cylindrical guide stud 83 (Figs. 1 and 2) is slidably disposed within the cylinder 88 and is threaded at its outer end 84 (Fig. 1) into a hole in larger segment I3.

The interior of the hollow cylinder 86 is lined with suitable bearing metal 85.

To aid in maintaining the segments in proper relation when in the expanded position, each end of each key segment is provided on its inside face with a small arcuate stop member 88 fastened thereto by means of a screw 89.

In order to impart the desired prole to the rim of the tire being built 'on the drum, the circumferential edges of the smaller segments are provided with arcuate turned-over rims 98 of suitable form and the edges of the larger segment are likewise provided with similar rims 9i. The rims are of the same arcuate length as the segments proper, and in no way interfere with expansion or collapse of the drum. The rims are constructed with an inner stepped portion 92 (Fig. 1) which its into the similarly stepped edge of each segment, the outer surface 93 of the rim forming a continuous smooth building surface with the surface of the drum segment. Attaching screws 94 passing through the rim member into the segments at a convenient angle in the manner shown permit easy removal of the rim members for substitution of differently shaped rims as desired.

As shown in Fig. 7, suitably shaped spacer members 96 of various widths, each of the same arcuate length as the segment to which it is attaehed, may be interposed between the rims and the segments for the purpose of building tires of various sizes on the one drum. The spacers and rims are easily assembled with the segments by means of machine screws 91 passing through the spacers into the segments, and machine screws 98 passing through the rims into the spacers vas shown.

Turning now to the details of the structure of the actuating plate 38 and the pneumatic actuating cylinder I8 associated therewith, it will be observed in Fig. lv that three fixed axially extending stop bolts |68 (two being shown) pass slidably through holes IUI in the axially movable plate 38, and are threaded through cylinder head 41 intojcorrespondingly threaded hole |82 in the'end of hub portion Il. Bushings |03 of suitable bearing metal are disposed within the holes IIlI. Nuts |84 on the threaded portion of the bolts |08 maintain the cylinder head 41 in place along with studs |33 on the end of the hub portion I1. The inner face of the vplate 38 isrecessed Las *at |05 to fprovide clearance ifor thenuts |04.`

When lthe-drum is-in collapsed condition, the heads |08 `of the boltsf|00 engage resilient Washr'ersor cushionsl |09 disposed within Yenlarged portions of the holes y||l| in the actuating platep38. Thus, `the heads ofthe bolts form stops for the plate 38, asindicated most clearlyfin'Fig. The positionof these-stops may be adjusted by threadling the bolts |80 into or out of the hub portion An annular axially projecting resilient Ycushion (Fig. l)` is'disposed partly Within a recess passing around the inner faceof theactu- `ating plate `near the periphery thereof. This resilient cushion ||0 engages the outer `face of cylinder `head `lll-when thedrum `is in expanded position.

Disposed `within the pneumatic actuatingcylinder is a Ypiston assembly ||5 which is con- `nectedby a piston rod llt to the actuating plate 38;? The piston rod fits intoa central recess il 1in, the-p1ate 38 and is fastened thereto by a bolt HB passing through `the `front of the plate into Ithe piston rod. A bolt H0. likewiselsecures the `piston rod H61 to the piston assembly H5. The passagefof the piston rod |16 throughthe cylin- `der Ahead f4? is sealed against air leakage by `a suitable packing-*ring |20, held in place by a cover plate Al|2| secured by 'screws |22 to thefronto theicylinder head. "Suitable packing |23 isalso provided around the perimeter-oi the piston assembly 5| 5. f

The hub I6 has a central axial passageway therethrough for introducing and removing compressed :air from the pneumaticcylinder I8. A `zzo-axial pipe |26 `within the passage |25 is `threaded linto a cylinderhead assembly |21 for `introducing air during the collapsing stroke of the Vpiston |I5. During the drum expanding stroke (movement from left to right in the drawings) of the piston ||5,the pipe |26 serves asv an exhaust channelforthe air, `while air is intro- Aduce'dlthrough axialpassageway |25 `in the hub, and thence through a passageway |28 drilled radially in the wall of hub portion l1, into a vpassage |29 drilled axially through the Wall of hub portion Il, and finally intoa passageway |30 drilled `radially through the cylinder head `4l, whence the air has access to the interior of the cylinder I8. The. ends of the drilled passage- `ways :|28 and |30 are sealed off from the outside atmosphere by tap screws |3| and |32 respectively.

As the `pistcn assembly ||5 approaches lthe cylinder head |21 on the expanding stroke, a `projecting.portion of the piston slides snugly into a central opening |36 in the cylinder head, thereby substantially sealing `oill said opening .against `further escape ofthe air in the cylinder. :An additional passage |31 throughthe cylinder head has therein Va one-way ball check valve vassembly |38 which-also preventsescapefof air.

Thereremains only Va small passageway |39 containing a restricted metering orifice M0, availablezforthe escape `of the remaining air toward the end of thepiston stroke.` Consequently, the `piston is slowed `down and pneumaticallycush- ,ioned tona gentle stop attbe end of its stroke,

' collapsing stroke, since the air introduced through pipe |26has access to substantially thelfull area of the face of thepiston through the central opening 38, the" passageway |39.: and the passageway ISLfwhich is .made available lay-automatic opening ofthe ball check valve |38 upon application y ci air pressure; A

In a similarmanner. a centralprojection |42 on the other end` ofthe piston H5, a ball check valve |43, and a metering .passageway (not shown) in cylinder head assembly 4T, cooperate to pneumatically cushion the piston at the end of the `collapsing stroke.

For-thc purpose of rotating the drum during thetire building operation in the usual manner, the end of the hub I6 sldetachably coupled to a shaft 150, of a conventional tire building machine (notrshown) by means of a coupling assembly `|5|. This `assembly-includes, on the end of Vthe hub |'6 a. central spider ring |52 having a core |53into which is threaded for support the end of `the central air :pipe |26. A washer or gasket 54 onV the `opposing face of a similar central air pipe |55, suitably supported in the center of -anvaxial .air passage |56 within the machine shaft |56, 'forms an-air-tight seal when the hub and shaft are drawn together. An outer resilient y,gasket `l5`| similarly seals the joint between the hub air passage |25 and the shaft air passage |55. It will be understood that theycompressed air may be `introduced into or removed from the pipe |55 and the passage |56 through the usual control valves land by the use of a conventional rotary seal coupling (not shown) conveniently located `at the `end of the shaft extending chine.

The central portion Vof the end of the machine :sha-M150 hasa projection |60 which seats in a corresponding center Ieounterbore in the end of thehub I6. The projection |50 acts as a register for centering the hub |6 with respect to the shaft |50 in assembly. l

For detachably securing the hub to the shaft there are provided Withinthe coupling assembly |5| a :plurality of axially extending studs IBI. Each` stud is securely threaded into the end of the `hub `Hiand is provided with a smooth cylindrical extension |62 which slides into a corresponding recess |63 in the machine shaft |5il.

`One sideof the cylindrical extension |62 has an arcuate flat `|64 (Fig. 3), against which a radially extending `eccentric |65 bears. The eccentric |65 is mounted in a recess |56 extendsion 1.62, therebydrawi-ng thelstud, and the hub AIiagainstthe shaft :|50 and effecting a positive lockfbetween `thehub and the shaft.

To disengagethehub 'fromthe shaft, itis simply necessary-toyturn fthe eccentric |64 in a counterclockwise direction, whereupon the stud |6| may be :withdrawn freely `from `the recess |63 in the `Shaft 50.

Theoperation of the collapsing and expandving mechanism .will now bedescribed. After a -tirelhasbeenbuilt or assembled on the cylindri- ,cal :surfaeexofttheiexpanded drum and it is desired tcl-remove `the tire `therefrom for further operations, such `as vacuum shaping and vulcanizing.: the collapse of the vdrum is initiated by admitting air through central pipe in the umachine :shaft 50 yand 'central pipe `|25 within ,the-hub ;|6. This-movesthespiston ||5 and the ,.pistonrod `||6 from `right toleft `as `ivievved in Fig. l, thereby Vmoving the actuating plate 38 axially on the bolts |00. The pivotal arms 35 move axially with the plate 3S, at the same time drawing the pivotal joint 35 between links 25 and 26 axially and radially, thereby collapsing the links 25 and 26 in a radially inward path lying in a plane parallel to the axis of the drum. As the toggle links 25 and 26 start to collapse, the key segments I6, II, and I2 pivotally attached to links 26 by pivot pins 33 begin to move inwardly. The inward movement of the key segments is rectilinear and radial, without any axial or rotary component of motion.

The inward movement of the key segments Ill, II and I2 causes, through the action of the pivotal auxiliary tie links 16, a tilting of the connecting yokes 53 about their fulcrums or pivot pins 55 in a counter-clockwise direction as viewed in Figs. 2 and 4. Such tilting of the yokes 53 is accompanied by clockwise rotation of the spider member 40 on which the yokes are pivotally mounted. Simultaneously, the connecting yokes 15 are tilted in a clockwise direction about their respective pivot pins, with consequent counter-clockwise rotation of the supporting spider 45.

The tilting ofr connecting yokes 53 and I5 initiates inward radial movement of the major segments I3, I4 and I5 pivotally joined thereto. As the key segments I6, II and I2 continue to move inward the larger segments I3, I4, and I5 continue to be drawn over them to a final collapsed position. At this time the actuating plate 36 engages the heads |08 of stop bolts |35, and the piston I I5 engages the cylinder head 41 as shown in Fig. 3. The larger segments are guided yor steadied in their inward radical movement by the telescoping studs 83 sliding within guide cylinders 86. The radial movement of the larger segments is also rectilinear, being without any axial or rotary component. In the collapsed position, as shown in Figs. 3 and 4, the yokes are folded compactly over the ends of the key segments and the larger segments are drawn in close proximity thereto in overlapping relation, to eiect a high degree of collapse.

The expansion of the drum is the opposite of the foregoing operation. Application of air pressure to the passageway |56 in the machine shaft |50 and the passageway |25 in the hub I6 causes the piston I I5 to move toward the cylinder head |21. This produces axial movement of the actuating plate 38 away from the 'heads of lthe stop bolts |05, and produces axial and outward radical movement of theV arm 36, thereby initiating, through the pivotal links 25 and 26, outward movement of the key segments'IO, II and I2. Movement of the key segments causes clockwise tilting of the yokes 53 about their pivot pins 55 with consequent counterclockwise rotation of the spider 40 with respect to the hub portion I1. Simultaneously the yokes 15 are tilted in a counter-clockwise direction and the supporting spider 46 likewise begins to revolve clockwise. Such tilting of the connecting yokes causes the larger segments I3, I4 and I5 to move outwardly radially until the stops 43 on the spiders 40 and 46 contact the stops 45 on the xed collar I9. Outward movement'of the key segments I0, II and I2 continues until the resilient cushion III] on the inner face of the actuating plate 38 engages the cylinder head 41.

The pivotal jointor fulcrum 55 of the connecting yokes `53 is so located that the initial inward .collapsing movement of the key segments does 8 not produce an immediate movement of the larger segments. This permits the key segments to clear the larger segments before inward movement of the latter is begun. Specifically, I locate the various stops, such as the stops -43,on the rotating spider member 40 and stops 45 -on the xed collar` I9 in such manner that when the drum is in the expanded condition the center of the fulcrum pin 55 of the connecting yoke 53 has traveled a small distance over or beyond the center line drawn from the center of the drum through the center of the pivot pin 63 which joins the yoke to the larger segment. This distance beyond center position represents the extent to which the pivot 63 may move in response to movement by the key segments without producing inward movement of the larger segments. Such over-center placement of the pivot 55 provides, in effect, for lost motion, or delay, in the inward movement of the larger segments so that the key segments are permitted to move clear of the larger segments and the latter are caused to follow the key segments without interference therewith. The pivots of all of the connecting yokes 53 and 'I5 are similarly disposed beyond their "center positions when the drum is in the expanded position. The fact that the pivots are so placed also establishes a positive locking of the larger segments in proper position, since small movements of the pivots which might be caused by vibration or the shock of starting or stopping the drum do not tend to cause collapse of the segments.

In like manner, I dispose the center of pivot pin 35 joining the links 25 and 26, which collapse the key segments, beyond a center line drawn through the centers of pivot 33 to the key segment and pivot 28 to the iixed collar when the drum is expanded. This over-center positioning of the pivot pin 35 is effected when the resilient .cushion I|0 on the inner face of the actuating plate 3B engages the cylinder head 41. This produces a positive locking action on the key segments so that they do not tend to collapse upon small movements of the links 25 and 26.

On the expansion stroke the fulcrum pins of the connecting yokes, such as pins 55 of the yokes 53, arrive at their over-center position, as determined by engagement of the stops 43 and 45, before the pivot pins 35 of the collapsing links associated with the key segments arrived at their over-center position, as determined by engagement of the resilient cushion stop III) on the actuating plate 38 with the cylinder head 41. Therefore, the larger segments are locked in the expanded position before the key segments have completed their expansion movement.l This has the desirable effect that no collapsing motion of ythe larger segments can take place until after the fulcrumed yokes attached thereto have been moved away from over-centerposition by the key segments. Hence, locking of the key segments in position when the drum is expanded effects a locking of the entire drum. The drum is therefore exceptionally stable in the expanded position, particularly against centrifulgal forces or rotary inertial forces occasioned by sudden starting, stopping, or reversing of the drum, since the key segments are collapsible only through an axially operable linkage.

From the foregoing, it is seen that I have provided a collapsible tire building drum in which the `various peripheral segments, when the drum is expanded, are positioned in a positively locked position, such positioning being determined by properly located stops, and being unaffected by any wear which might occur on various parts of the collapsing linkages.

Also, I have provided a drum'in which the actuating mechanism operates essentially axially of the drum, and is therefore relatively unaffected by the rotation of the drum, sothatexpansion and collapse may be effected. with equal ease while the drum is rotating in either direction or While the drum is stationary. Sudden starting or stopping of the drum. does not tend tocause expansion or collapse.

I have disposed the various segments-'and col's lapsing members symmetrically with respectto the drum axis and with respect' to the transverse center line of the drum, so thattheparts are largely interchangeable. Thus, for example, if it becomes necessary togrepair any one of the key segments, a single spare key segment willvserve as a substitute for any oi the-key segments-IIJ, l I or l2. Therefore, it is possible to `maintain a number of such drums in continuous` operation with a' minimum number of'spare` parts.

Because of the way individual rims are detachably mounted on the edges of eacliof the segments, tires with a variety of rim profiles may be constructed on the one drum by substituting rims of different contours'. The.` rims in no way interfere with expansion or collapse of the drum,

and they may beu changed when the drum is in either the expanded or collapsed position, without removing the drum from the* machine. In the same way, detachable' spacers may be interposed between the rims and the segments to vary the width of the drum surface, while still retaining a smooth uninterrupted building surface. Equal sized spacers may be` placed on each side of the drum, so that the symmetry and balance of the drum is not disturbed, Since the center line of the drum is not disturbedtheV usual adjacent auxiliary equipment remains in proper alignment with respect to the drum as the width thereof is changed by this method.

By locating the actuating means, sucli asia pneumatic cylinder; within the hub of the drum, I have provided a seli-contained unit that can be easily attached to a` conventionaltire `building machine. Various sizes of drums containing such internal actuating means can beA attached conveniently to the tire building machine.

The various cushioning means associated" with the collapsing structure, particularly thepneumatic cushioning means provided ateachendof the stroke of the actuating piston,permit rapid expansion and collapse or" the drum without shock or strain on the drum parts.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. A collapsible building drum comprising in combination a hub, a` set of key segments, an actuating member connected between said hub and key segments for drawing'said keysegme'nts radially inwardly, a set of intermediate segments, pivotal links joining said key segments to `said intermediate segments for drawingr said intermediate segments inwardly over said key .segments, and collars pivoted to said links and mounted for limited rotation about said hub for controlling the motion of said intermediate'sege ments.

2. A collapsible drum comprising a hub,` ais'et of key segments and a set of larger segments alternately placed with respect to said" key segments, a toggle linkage actuated axially ofthe drum secured only toxthe: saidkeysegments-to l0 pun saidfkey sesrentsradialiyinwardly with res'pect-toithef hub' inla rectilinear path, pivotal linkages connecting said key segments to said larger segments for drawingthelarger segments inwardly radially over the key segments; said pivotal linkagesbei'ng fulcrumed on spider mem# bers mounted for limited rotationaboutsa'ld hub.

3. A collapsible building drum comprising! a hub, an actuating cylinder within said hub, a. collapsing linkage actuated axially by said'cylinder, a set of peripheral key drum segments mounted on said' hubfor inward and outward radialmovement by said collapsing linkage, 'a set oi"V peripheral larger drum1 segments pivotally connected to Asaid key segments and movable in 'wardlyA or outwardlyradially with movement A'of said-key segments` and mearistfor` limiting the movement of said larger segments to movement in a' direction purely radially of saidhub.

4. A` collapsible building drumcomprising a hub, a set of key' members and a set of larger membersalternately placed with respect to said key members,` collapsing' means for eaiclr key member actuated axially of said hub and com prising a link, a' pivotal joint connecting said link tosaid key member, a second link, a pivotalp'oint connecting said second link to said hub, and a connecting pivotal joint'joining the said two links; means for positioning the'said connecting pivotal joint beyonda center line drawn between the said pivotal* joint to the key member and the said pivotal joint to* the hub when the" drum is in the-expanded position, whereby the key mem'-i bers are positively maintained in position; the said keymembers being pivotally linked to" said larger members to draw the said larger members inwardly radially after thekey me'nlbersup'onacr-a tuation of the said collapsing means and the pive otalilinks joining the key members to' the larger members being linked to members mounted for rotation about the hub but immovable axially, wherebycollapsing movement of the'segmentsis limited toradial movement.

5. A drurnvcomprising a central hub, a set'rof smaller sections and a set of larger sections alternately placedwitli respect to said-smaller sections, an axially movable-toggle linkage connected to saidsmaller'sections for drawingsaid smaller sections inwardly to collapse the drum, and means forv drawing said larger sections inwardly Vraulially over said smaller sections comprisingV yokes conneoting the larger sections to' the smaller sectionseach of said'yokes being. connected to one ofz said larger sections by a pivotal joint, and each yoke being"` connected by a pivotal fulcrum to a spider mounted for` limited rotation about saidv hub, and stops on said` spider for position-i ing. the center of` saidlipivotal fulcrum beyond a center line drawn-between said pivotal joint and thesaidhub whenthe drum isin the expanded position, whereby the larger sectionsa're positively maintained in position.

6r Aibuilding drum `comprising a hub,` a set/of key members, atogglelinkage for collapsing said key mcmbersradially, means movable axially of said hub for actuating'isaidwtogglel linkage, aston' on said hub contacting said actuatingmeans when the' drum is expanded for locating. said toggle linkage in al positively lockediposition when the drum4 is expandeda set ofilargerimembers, controlyokesjciningfsaid` larger members to said key membersfonraclialmovement oversaid key members upon collapsingV the drum; `guiding measdfor said control yokes,` andstops contactixi-icooperating'stops on. saidguiding means when l l the drum is expanded for maintaining said larger members in a positively locked position when the drum is expanded.

'7. A collapsible tire building drum comprising a hub, a set of key segments collapsible radially and a set of larger segments linked to said key segments for inward radial movement over said key segments, means for collapsing said key segments, each segment comprising a single body presenting a smooth outer working surface of definite width, the lateral edges of each segment having a stepped portion, a cooperating spacer piece having a corresponding stepped edge fitting into the lateral edge of each segment and forming a smooth continuation of the smooth working surface of such segment, the outer edge of the spacer piece being stepped similarly to the said stepped edge of the segment, a cooperating rim piece having a correspondingly stepped inner edge iitting into said outer'edge of the spacer piece, means for detachablysecuring the spacer piece to the segment, and means for de tachably securing the rimportion to the spacer piece.

8. A collapsible drum comprising a hub,'a set of key segments collapsible radially, means actuated axially of saidhub for collapsing said key segments, a set of larger segments alternately placed with respect to said key segments, means for drawing said larger segments inwardly radially over said smaller segments comprising connecting yokes pivotally connected to the larger segments and pivotally connected to the smaller segments, a collar for pivotally Asupporting and guiding said yokes, said collar being mounted for limited rotation about the said hub, and stops projecting from the hub for definitely locating said collar, when the drum is fully expanded, at a point suchthat the initial inward movement of the key segments in collapsing the drum produces motion of the said connecting yokes and rotatable collar without collapsing the larger segments, and continued inward movement of the key segments causes the larger segments to be drawn inwardly over the key segments in a path controlled by the said connecting yokes and rtatable collar. YV9. A collapsible building drum comprising a hub, a set of key segments, a toggle linkage for collapsing land expanding said key segments radially, means actuatedv axially of the hub for operating said toggle linkage, a set of larger segments alternately disposed with respect to said key segments. means for actuating said larger segments comprising, rotatable spiders located at spaced points along said hub, ilxed stops on the said hub cooperating with stops on said spider for limiting the rotation of said spiders, a plurality of connecting yokes pivotally mounted on said spiders, each yoke being pivotally joined to a key segment and pivotally joined to a larger segment adjacent said key segment so that inward movement of the.key segment causes the larger segments to be drawn inwardly radially over the key segments by the pivotal connecting yokes, the pivoting of the connecting yokes being accompanied by rotation of the said rotatable spiders so that the path and extent of travel of the larger segments is thereby controlled, said rotatable collars rotating in opposite directions with respect to each other during expansion and collapse of the drum, so that the said expansion and collapse is essentialy uninfiuenced by the rotation of the drum.

l0. A building form comprising a hub, al set of ley members, a togglelinkage cpnnectingsaid keyv members to said hubfor collapsinga'nd expanding said key members radially, a pneumatically actuated piston within said hub for operating said toggle linkage in a direction axially of said hub to collapse and expand the form, means for pneumatically cushioning said piston at each end of its stroke in operating said toggle linkage, a set of larger members alternately placed with respect to said key members, pivotal connecting links connecting said larger members to said key members for drawing said larger members inwardly after said key members in collapsing the form, and means for controlling the motion of said larger members including a member mounted for limited rotation about said hub and pivotally supporting said pivotal connecting links.

l1. A building drum adapted to beV expanded and collapsed comprising a hub, a set ofarcuate key segments connected to said hub by a pivotal collapsing and expanding linkage, a set of arcuate larger'segments connected to said key seg` ments by a connecting pivotal collapsing and expanding linkage operable by movement of said key segments, Said connecting linkage also being connectedto guiding means supported on said hub, and said key segments and said larger segments forming a cylindrical building surface when the drum is in the expanded position, axially operable means for actuating said first mentioned linkage to expand and collapse said key segments,` a stop associated with said hub engaging cooperating stops on said guiding means for said connecting linkage when the larger segments are in the expanded position, said stop being so located that the said pivotal connecting linkage controlling said larger segments is disposed in a positively locked overcenter position when the larger segments are in the expanded position, and a stop associated with said hub engaging said actuating means when the key segments are in the expanded position, said stop being so located that the pivotal expanding linkage controlling the key segments is disposed in a positively locked over-center position when the key segments are in the expanded position, the relation of the said stops to the said guiding means and the said actuating means being such that on expanding the drum the stop controlling the position of guiding means for the larger segments is engaged by the guiding means before the stop controlling the position of the key segments is engaged by the actuating means for the key segments.

12. A collapsible building drum comprising in combination a hub, a rst set of arcuate segments, axially operated toggle linkages for drawing said rst segments inwardly toward said hub, further pivotal linkages between said hub and first segments movable radially but immovable axially whereby inward movement of said first segments is confined to purely radial movement, a further set of arcuate segments intermediate said rst segments, said further pivotal linkages .being pivotally attached to said intermediate segments to draw said intermediate segments inwardly with said rst segments.

i3. A collapsible building drum comprising in combination a hub, a first set oi arcuate segments, a second set of intermediate arcuate segments, toggle linkages arranged in a plane parallel to the axis of the drum for collapsing movement in said plane, said toggle linkages being connected between said rst segments and said hub. an axially movable member for collapsing said toggle linkages to draw the first segments 13 toward the hub, pivotal links between the second segments and the rst segments to draw the second segments inwardly with the rst segments, and pivotal links movable only in a plane transverse to the axis of the drum connected to said segments for restricting the collapsing movement of the segments to purely radial movement.

14. A collapsible building drum comprising in combination a hub, a rst set of arcuate segments, a second set of intermediate arcuate segments, toggle linkages arranged in a plane parallel to the axis of the drum for collapsing movement in said plane, said toggle linkages being connected between said rst segments and said hub, an axially movable member for collapsing said toggle linkages to draw the rst segments toward the hub, pivotal links between the second segments and the first segments to draw the second segments inwardly with the first segments, further pivotal links movable only in a plane transverse to the axis of the drum connected to said segments for restricting the collapsing movement of the segments and a ra.- dially telescoping guide xed to the hub and to the segments for further steadying and guiding the segments in a purely radial collapsing path.

HOLLIS C. HODGKINS.

REFERENCES CITED The following references are of record in the ile of this patent:

UNITED STATES PATENTS Number Name Date 1,434,567 Smith et al. Nov. 7, 1922 1,481,850 Midgley Jan. 29, 1924 1,558,603 Fleiter Oct. 27, 1925 1,877,746 Heston et al Sept. 13, 1932 2,201,468 Bostwick May 21, 1940 2,201,469 Bostwick May 21, 1940 

